A die-rotating system was proposed in this work for moderations of extrusion forces and entrance pressure drop for molten polypropylene (PP) and wood/ polypropylene (WPP) composites in a capillary rheometer and a single screw extruder. The effects of processing conditions and wood loading in PP were of our interests. The extrusion force and entrance pressure drop with and without the die rotating system were monitored in real-time. This was the first time that the die-rotating system was used for processing of highly viscous wood/polymer composite materials. It was found that the flow properties of the molten PP and WPP composites obeyed pseudoplastic non-Newtonian behavior. The behavior was more obvious at wood contents of above 6 wt % and in the capillary rheometer. The rotation of the die could moderate the extrusion load by 60% and entrance pressure drop by 20% in the capillary rheometer, and the entrance pressure drop by 30% in the single screw extruder, especially at the conditions where the viscosities of the WPP and the extrusion rate were high. Greater fluctuations in entrance pressure drop caused by die rotation were observed in the single screw extruder.
Studies into the properties of polymer-wood composites (PWC) are mostly focused on thermoplastics as the matrix phase and wood flour as a reinforcing phase. This article aims to identify the optimum contents of wood sawdust fibre and silane coupling agent to be introduced into natural rubber (NR) compounded with carbon black (CB). The authors have considered a wide range of composite properties, including cure characteristics, % bound rubber, crosslink density, sorption and desorption behaviour, tensile modulus, elongation at break, tensile and tear strengths, hardness, and morphological properties. The results suggest that the overall mechanical properties of the NR composites improved with increasing CB content, but deteriorated sharply with sawdust content up to 40 phr. Addition of further sawdust was recommended as an economical benefit to industries as the properties of the NR/CB composites remained unchanged with increasing sawdust content above 40 phr sawdust fibre.
Addition of N-(βaminoethyl)-γ-aminopropyl-trimethoxy silane coupling agent to the NR vulcanisates, containing 40 phr of wood sawdust fibres and 45 phr carbon black at 0.5-1.0 %wt of wood sawdust, improved the mechanical properties. The explanations for the results given in this paper are unique in that they refer to bound rubber, crosslink density and rubber-filler phase continuity in the composites, and to a change in composite rigidity.
Purple rice (Oryza sativa L.) is popular for planting and consuming in North and Northeast Thailand. The important pigment on the purple rice grain is anthocyanin which has high antioxidant activity. This research studied the effect of applying a pulse electric field (PEF) technique on the extraction of the total anthocyanin content, and the antioxidant activity of purple rice. The extraction treatment was divided into two levels of PEF [low and high PEF]. The low PEF treatment condition used low pulse numbers (0, 100, 300, and 500) at three levels of electric field intensity (2, 3, and 4 kilovolts / centimetres (kV cm–1) in 1 Hz). The high treatment condition used an electric field intensity of 6 kV cm–1 in 1 Hz with the pulse numbers of 1,000, 3,000, 4,000, and 5,000. The results indicated that a sample extracted with low PEF showed low anthocyanin content but high % of DPPH inhibition. In contrast, a high level of anthocyanin content and low % of DPPH inhibition were found in the high PEF extraction treatment. The result demonstrated that PEF technology did not cause a chemical change to anthocyanin but affected antioxidant activity. This effect was due to high energy and temperature generated in the high PEF treatment. The PEF technique has a benefit in decreasing the time required for the extraction process and does not negatively affect the anthocyanin extracted. The appropriate PEF extraction condition for purple rice was obtained at 6 kV cm–1 with 3,000 pulses, which provided an acceptable total anthocyanin content (2.50 ± 0.09 mg l–1) and was consistent with a percent inhibition of DPPH (60.97 ± 0.64). The results of this study have implications for the ongoing development and use of food-based products.
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